diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
new file mode 100644
index 00000000..1eb59a05
--- /dev/null
+++ b/.github/CODEOWNERS
@@ -0,0 +1,4 @@
+# craft-proof moved here from WordCraft's crates/proof; the WordCraft maintainers own it.
+# Confirm these handles before merge (WordCraft has no CODEOWNERS file to copy from).
+/crates/proof/ @dylanmtaylor @aiongg @skylartaylor
+/.github/workflows/proof.yml @dylanmtaylor @aiongg @skylartaylor
diff --git a/.github/workflows/proof.yml b/.github/workflows/proof.yml
new file mode 100644
index 00000000..db171ee1
--- /dev/null
+++ b/.github/workflows/proof.yml
@@ -0,0 +1,60 @@
+name: Proofing
+
+on:
+  push:
+    branches: [main]
+    paths: ["crates/proof/**", "Cargo.toml", "Cargo.lock", ".github/workflows/proof.yml"]
+  pull_request:
+    paths: ["crates/proof/**", "Cargo.toml", "Cargo.lock", ".github/workflows/proof.yml"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: craft-proof-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    timeout-minutes: 20
+    name: Proofing lint, tests with and without Language data, WASM
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      # The Language data (craft-i18n `language-data/`), embedded by crates/proof/build.rs.
+      # TODO(CP1.2): pin `ref` to the craft-i18n commit that adds language-data/ once it merges.
+      - uses: actions/checkout@v4
+        with:
+          repository: storytold/craft-i18n
+          path: craft-i18n
+          persist-credentials: false
+      - uses: dtolnay/rust-toolchain@b725eda525362e7cf34af9a7243cac1e3f01a7ec # stable
+        with:
+          components: rustfmt, clippy
+          targets: wasm32-unknown-unknown
+      - uses: Swatinem/rust-cache@d1527c8f67ef9af357290475d4af4b0fab8f12e0 # v2.9.3
+        with:
+          key: craft-proof
+      - run: cargo fmt -p craft-proof --check
+      - name: Without Language data (a fork, docs.rs, offline)
+        run: |
+          cargo clippy -p craft-proof --all-targets --locked -- -D warnings
+          cargo test -p craft-proof --locked
+          cargo check -p craft-proof --locked --target wasm32-unknown-unknown
+      - name: A release without Language data fails
+        run: |
+          if CRAFT_I18N_REQUIRED=1 cargo check -p craft-proof --locked 2>build.log; then
+            echo "::error::CRAFT_I18N_REQUIRED=1 without CRAFT_I18N_DIR built"; exit 1
+          fi
+          grep -q "CRAFT_I18N_REQUIRED=1 but CRAFT_I18N_DIR is unset" build.log
+      - name: With Language data
+        env:
+          CRAFT_I18N_DIR: ${{ github.workspace }}/craft-i18n
+          CRAFT_I18N_REQUIRED: "1"
+        run: |
+          cargo clippy -p craft-proof --all-targets --locked -- -D warnings
+          cargo test -p craft-proof --locked
+          cargo check -p craft-proof --locked --target wasm32-unknown-unknown
diff --git a/Cargo.lock b/Cargo.lock
index 4fcd223b..368a83a6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1002,6 +1002,16 @@ dependencies = [
  "winsafe",
 ]
 
+[[package]]
+name = "craft-proof"
+version = "0.1.0"
+dependencies = [
+ "log",
+ "miniz_oxide 0.9.1",
+ "proptest",
+ "unicode-normalization",
+]
+
 [[package]]
 name = "craft-quit"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index a98e231b..3946fd50 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -39,6 +39,7 @@ craft-media = { path = "crates/media" }
 craft-menu = { path = "crates/menu" }
 craft-prepress = { path = "crates/prepress" }
 craft-print = { path = "crates/print" }
+craft-proof = { path = "crates/proof" }
 craft-quit = { path = "crates/quit" }
 craft-settings = { path = "crates/settings" }
 craft-text = { path = "crates/text" }
diff --git a/README.md b/README.md
index 30d08db6..58b561d6 100644
--- a/README.md
+++ b/README.md
@@ -81,6 +81,9 @@ craft-<name> = { git = "https://github.com/storytold/craft-libs", rev = "<commit
   stay in each app.
 - [`craft-print`](crates/print/README.md): PDF submission to CUPS and Windows, printer discovery,
   duplex/copies/colour and driver preferences. PDF generation stays in each app.
+- [`craft-proof`](crates/proof/README.md): proofing per language (spelling, suggestions, grammar,
+  hyphenation, a Hunspell reader, user words). The word lists and patterns are craft-i18n's
+  `language-data/`, embedded at build time from `CRAFT_I18N_DIR`.
 
 - [`craft-quit`](crates/quit/src/lib.rs): native macOS quit, egui close handling and an optional
   app menu. Unsaved-document decisions and save prompts stay in each app.
diff --git a/crates/proof/Cargo.toml b/crates/proof/Cargo.toml
index 4c1a5b11..f94b54e8 100644
--- a/crates/proof/Cargo.toml
+++ b/crates/proof/Cargo.toml
@@ -1,15 +1,18 @@
 [package]
-name = "wordcraft-proof"
+name = "craft-proof"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
-description = "WordCraft proofing per language: spelling, suggestions, grammar checks and hyphenation for English (public-domain word list) and Polish (installed Hunspell dictionary, TeX patterns)"
+rust-version.workspace = true
+repository.workspace = true
+description = "Proofing per language for the Craft Apps: spelling, suggestions, grammar checks and hyphenation, a Hunspell .aff/.dic reader, and user and ignored words. Language data is embedded from craft-i18n at build time (CRAFT_I18N_DIR)."
+build = "build.rs"
 
 [lints]
 workspace = true
 
 [dependencies]
-log = { workspace = true }
+log = "0.4"
 miniz_oxide = "0.9"
 unicode-normalization = "0.1"
 
diff --git a/crates/proof/README.md b/crates/proof/README.md
new file mode 100644
index 00000000..34e2669f
--- /dev/null
+++ b/crates/proof/README.md
@@ -0,0 +1,70 @@
+# craft-proof
+
+Proofing for the Craft apps, per language: spelling, suggestions, grammar checks and hyphenation,
+a Hunspell `.aff`/`.dic` reader, user words, ignored words and a dictionaries folder. It moved here
+from WordCraft's `wordcraft-proof` with its history and the same public API. No `unsafe`, no
+panics on hostile input, and it builds for `wasm32-unknown-unknown`.
+
+```toml
+craft-proof = { git = "https://github.com/storytold/craft-libs", rev = "<commit>" }
+```
+
+## Languages
+
+| Language | Spelling | Grammar | Hyphenation |
+|---|---|---|---|
+| English (en-US, en-GB and the British-spelling Englishes, en-CA) | Moby word list + `en-extra.txt`, dialect variants (`en-variants.txt`) | yes | Moby list, our patterns, heuristic |
+| Polish, Portuguese, Italian | the installed Hunspell dictionary | yes | TeX patterns |
+| Croatian, Turkish, Russian, Czech, Indonesian, Spanish (es, es-MX, es-419, es-UY) | the installed Hunspell dictionary (Russian also `ru-extra.txt`) | yes | Turkish and Russian rules; English fallback otherwise |
+| German | — | — | TeX patterns |
+| Bulgarian | — | — | syllable rules |
+
+Grammar rules, suggestion tuning and the rule-based hyphenation are code: they work in every
+build.
+
+## Use
+
+```rust
+use craft_proof::{ProofLang, check_text_with, suggest_in, Options};
+use craft_proof::hyphen::{hyphen_points_in, Limits};
+
+// A paragraph whose runs are in different languages (byte ranges of `text`).
+let issues = check_text_with(text, &[(0..text.len(), ProofLang::EnGb)], &Options::default(), true, false);
+let fixes = suggest_in("colour", 5, ProofLang::En);
+let breaks = hyphen_points_in("hyphenation", &Limits::default(), ProofLang::En);
+```
+
+State is process-wide: `add_word`, `ignore_word`, `set_dictionaries_folder`,
+`load_user_dictionary`/`save_user_dictionary`. The crate reads no document model; callers pass
+plain text and language spans.
+
+## Language data
+
+The word lists and patterns live in [craft-i18n](https://github.com/storytold/craft-i18n)
+(`language-data/`), not here. `build.rs` embeds them at build time:
+
+- `CRAFT_I18N_DIR=<absolute path to a craft-i18n checkout>` embeds `language-data/`.
+- Unset (a fork, docs.rs, offline): the crate builds with a warning and no embedded Language
+  data. English spelling then marks nothing and suggests nothing, and hyphenation that needs the
+  data is off; grammar and the Hunspell languages work as before.
+- `CRAFT_I18N_REQUIRED=1` (releases) makes a missing directory or file an error.
+
+Tests that pin results of the data are ignored without it; `src/no_data.rs` runs every public
+entry point with no data embedded.
+
+## Check
+
+```sh
+cargo fmt -p craft-proof --check
+cargo clippy -p craft-proof --all-targets -- -D warnings
+CRAFT_I18N_DIR=/abs/path/craft-i18n cargo test -p craft-proof
+cargo test -p craft-proof   # without Language data
+cargo check -p craft-proof --target wasm32-unknown-unknown
+```
+
+CI: `.github/workflows/proof.yml`.
+
+## Licence
+
+MIT OR Apache-2.0. The Language data carries its own licences, recorded in craft-i18n's
+`ATTRIBUTION.md`.
diff --git a/crates/proof/build.rs b/crates/proof/build.rs
new file mode 100644
index 00000000..2620e54f
--- /dev/null
+++ b/crates/proof/build.rs
@@ -0,0 +1,97 @@
+//! Embed the Language data from a craft-i18n checkout (storytold/craft-i18n, `language-data/`).
+//!
+//! `CRAFT_I18N_DIR`, an absolute path to a craft-i18n checkout: `$OUT_DIR/language_data.rs` holds
+//! one constant per file in [`FILES`], each an `include_str!`/`include_bytes!` of
+//! `$CRAFT_I18N_DIR/language-data/<path>`. Unset, or not a checkout, or a file missing (a warning):
+//! that constant is empty, and the crate has no embedded Language data for it (English spelling
+//! marks nothing, hyphenation that needs the data is off). With `CRAFT_I18N_REQUIRED=1` (releases)
+//! any of those is an error instead.
+//!
+//! When the English word list is embedded, the `craft_proof_data` cfg is set (the tests that pin
+//! results of the data use it).
+
+use std::fmt::Write as _;
+use std::path::{Path, PathBuf};
+
+/// (constant, path under `language-data/`, bytes rather than text).
+const FILES: &[(&str, &str, bool)] = &[
+    ("EN_US_DIC", "en-us/en-us.dic", true),
+    ("EN_US_PAT", "en-us/en-us.pat", false),
+    ("EXTRA_EN", "en-us/en-extra.txt", false),
+    ("EN_VARIANTS", "en-us/en-variants.txt", false),
+    ("PL_PAT", "pl/pl.pat", false),
+    ("PT_PAT", "pt/pt.pat", false),
+    ("IT_PAT", "it/it.pat", false),
+    ("DE_PAT", "de/de.pat", false),
+    ("EXTRA_RU", "ru/ru-extra.txt", false),
+];
+
+fn main() {
+    println!("cargo::rerun-if-changed=build.rs");
+    println!("cargo::rerun-if-env-changed=CRAFT_I18N_DIR");
+    println!("cargo::rerun-if-env-changed=CRAFT_I18N_REQUIRED");
+    println!("cargo::rustc-check-cfg=cfg(craft_proof_data)");
+    let required = std::env::var("CRAFT_I18N_REQUIRED").is_ok_and(|v| v.trim() == "1");
+    let level = if required { "error" } else { "warning" };
+    let dir = match std::env::var_os("CRAFT_I18N_DIR").filter(|d| !d.is_empty()) {
+        Some(d) => match language_data(&PathBuf::from(d)) {
+            Ok(dir) => Some(dir),
+            Err(e) => {
+                println!("cargo::{level}=CRAFT_I18N_DIR: {e}; craft-proof embeds no Language data");
+                None
+            }
+        },
+        None => {
+            if required {
+                println!("cargo::error=CRAFT_I18N_REQUIRED=1 but CRAFT_I18N_DIR is unset: a release must embed the Language data");
+            } else {
+                println!("cargo::warning=CRAFT_I18N_DIR is unset: craft-proof embeds no Language data (no English spelling marks, no hyphenation)");
+            }
+            None
+        }
+    };
+    let mut o = String::from("// Generated by craft-proof's build.rs from CRAFT_I18N_DIR/language-data. Do not edit.\n");
+    let mut english = false;
+    for &(name, rel, bytes) in FILES {
+        let file = dir.as_ref().map(|d| d.join(rel)).filter(|f| f.is_file());
+        if let (Some(d), None) = (&dir, &file) {
+            println!("cargo::{level}=CRAFT_I18N_DIR: {} is missing; craft-proof embeds none", d.join(rel).display());
+        }
+        let (ty, empty, mac) = if bytes { ("&[u8]", "b\"\"", "include_bytes") } else { ("&str", "\"\"", "include_str") };
+        let value = match &file {
+            Some(f) => {
+                println!("cargo::rerun-if-changed={}", f.display());
+                if name == "EN_US_DIC" {
+                    english = true;
+                }
+                // `{:?}` escapes the path (Windows backslashes) as a Rust string literal.
+                format!("{mac}!({:?})", f.display().to_string())
+            }
+            None => empty.to_string(),
+        };
+        let _ = writeln!(o, "/// `language-data/{rel}` (empty when it isn't embedded).\npub(crate) static {name}: {ty} = {value};");
+    }
+    if english {
+        println!("cargo::rustc-cfg=craft_proof_data");
+    }
+    let out = PathBuf::from(std::env::var_os("OUT_DIR").unwrap_or_default()).join("language_data.rs");
+    if let Err(e) = std::fs::write(&out, o) {
+        println!("cargo::error=writing {}: {e}", out.display());
+    }
+}
+
+/// `dir/language-data`, when `dir` is an absolute path to a checkout that has one.
+fn language_data(dir: &Path) -> Result<PathBuf, String> {
+    // Build scripts run in the crate's directory and `include_str!` resolves against the generated
+    // file, so a relative path would mean two different places. Not canonicalized: on Windows that
+    // gives `\\?\C:\…`, which `include_str!` can't read.
+    if !dir.is_absolute() {
+        return Err(format!("{} is not an absolute path", dir.display()));
+    }
+    let data = dir.join("language-data");
+    if !data.is_dir() {
+        return Err(format!("{} has no language-data/ (a craft-i18n checkout older than its Language data?)", dir.display()));
+    }
+    println!("cargo::rerun-if-changed={}", data.display());
+    Ok(data)
+}
diff --git a/crates/proof/src/dict.rs b/crates/proof/src/dict.rs
index 81eb0de1..3bcedb0b 100644
--- a/crates/proof/src/dict.rs
+++ b/crates/proof/src/dict.rs
@@ -1,6 +1,6 @@
 //! Hyphenation exception dictionary: lowercase words with their break points.
 //!
-//! On-disk format (`assets/hyphenation/en-us.dic`): raw-deflate of
+//! On-disk format (craft-i18n's `language-data/en-us/en-us.dic`): raw-deflate of
 //! `"DCHYPH1\n"` followed by one line per word, sorted by the plain word's bytes. Each line is
 //! front-coded against the previous one: a byte with the shared prefix length (in bytes of the
 //! hyphenated form), then the rest of the hyphenated form (`-` at every break), then `\n`.
@@ -165,6 +165,7 @@ mod tests {
         assert!(back.get("dog").is_none());
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn oversized_data_is_refused() {
         const LIMIT: usize = 1 << 16;
diff --git a/crates/proof/src/en_variants.rs b/crates/proof/src/en_variants.rs
index 56b9f26f..07c16bb1 100644
--- a/crates/proof/src/en_variants.rs
+++ b/crates/proof/src/en_variants.rs
@@ -2,7 +2,7 @@
 //! English ([`ProofLang::En`], [`ProofLang::EnCa`], [`ProofLang::EnGb`]) accepts, which it flags,
 //! and what it suggests instead (`colour` → `color` in American English).
 //!
-//! The pairs come from `assets/spelling/en-variants.txt`, our own list of base forms with a
+//! The pairs come from craft-i18n's `language-data/en-us/en-variants.txt`, our own list of base forms with a
 //! policy per English. Inflections are generated here by rule for the regular patterns (-or/-our,
 //! -er/-re, -ize/-ise, -ense/-ence…), so `colours`, `centred` and `organisation` follow their
 //! base forms. A form is right when the shared English word list knows it or knows its other
@@ -15,7 +15,7 @@ use std::sync::OnceLock;
 use crate::ProofLang;
 
 /// Our list of American/British pairs: `POLICY AMERICAN BRITISH` per line, `#` comments.
-const VARIANTS: &str = include_str!("../../../assets/spelling/en-variants.txt");
+use crate::data::EN_VARIANTS as VARIANTS;
 
 /// What one English does with a pair's two spellings.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -217,6 +217,7 @@ pub fn is_foreign(lower: &str, lang: ProofLang) -> bool {
 mod tests {
     use super::*;
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn every_line_parses() {
         let lines = VARIANTS.lines().map(str::trim).filter(|l| !l.is_empty() && !l.starts_with('#')).count();
diff --git a/crates/proof/src/es/grammar.rs b/crates/proof/src/es/grammar.rs
index 614a1f07..15806edb 100644
--- a/crates/proof/src/es/grammar.rs
+++ b/crates/proof/src/es/grammar.rs
@@ -336,7 +336,9 @@ mod tests {
     /// About 99 KB (under the 100,000-byte paragraph cap) took hundreds of milliseconds; it is now
     /// O(n log m): about 1 to 5 ms in a debug build, against about 300 ms for the scan, so the
     /// bound below leaves room on a loaded machine and still catches a return to the quadratic
-    /// lookup.
+    /// lookup. craft-libs builds tests at `opt-level = 0` (WordCraft used 1), where the linear
+    /// lookup took up to ~80 ms under a parallel test run, so the bound is 150 ms.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn many_addresses_before_a_question_are_checked_quickly() {
         for (unit, ending, whole_paragraph) in
@@ -348,7 +350,7 @@ mod tests {
             let started = std::time::Instant::now();
             let issues = check(&text, ProofLang::Es);
             let took = started.elapsed();
-            assert!(took < std::time::Duration::from_millis(75), "{unit:?} took {took:?}");
+            assert!(took < std::time::Duration::from_millis(150), "{unit:?} took {took:?}");
             let missing: Vec<&Issue> = issues.iter().filter(|i| i.message.starts_with("Falta")).collect();
             assert_eq!(missing.len(), 1, "{unit:?}: {missing:?}");
             // The mark's sentence is the whole paragraph when the addresses don't end with a mark
diff --git a/crates/proof/src/hyphen.rs b/crates/proof/src/hyphen.rs
index b203ff1a..60f4269c 100644
--- a/crates/proof/src/hyphen.rs
+++ b/crates/proof/src/hyphen.rs
@@ -3,7 +3,7 @@
 //! **English** (and languages without patterns of their own, as before languages were told
 //! apart), lookup order for each word:
 //! 1. the **dictionary** ([`Dictionary::en_us`]) — the public-domain Moby Hyphenator II word list
-//!    by Grady Ward (~160k words), stored compactly in `assets/hyphenation/en-us.dic`; simple
+//!    by Grady Ward (~160k words), stored compactly in craft-i18n's `language-data/en-us/en-us.dic`; simple
 //!    inflections (`'s`, `-s`, `-es`, `-ed`, `-d`) inherit the breaks of their stem;
 //! 2. **Liang patterns** ([`Patterns::en_us`]) for words not in the dictionary — our own pattern
 //!    set, trained from the same list by DesignCraft's patgen (generated by DesignCraft's `hyphgen` example);
@@ -30,18 +30,10 @@ pub use crate::lang::ProofLang;
 pub use dict::Dictionary;
 pub use patterns::Patterns;
 
-static EN_US_DIC: &[u8] = include_bytes!("../../../assets/hyphenation/en-us.dic");
-static EN_US_PAT: &str = include_str!("../../../assets/hyphenation/en-us.pat");
-/// hyph-utf8's `hyph-pl.tex`, unmodified (its licence header is in the file).
-static PL_PAT: &str = include_str!("../../../assets/hyphenation/pl.pat");
-/// hyph-utf8's `hyph-pt.tex`, unmodified (its BSD 3-clause header is in the file).
-static PT_PAT: &str = include_str!("../../../assets/hyphenation/pt.pat");
-/// hyph-utf8's `hyph-it.tex`, unmodified (offered under MIT or LPPL; WordCraft uses MIT, whose
-/// notice is in the file's header).
-static IT_PAT: &str = include_str!("../../../assets/hyphenation/it.pat");
-/// hyph-utf8's `hyph-de-1996.tex` (reformed spelling), unmodified (MIT; the notice is in the
-/// file's header).
-static DE_PAT: &str = include_str!("../../../assets/hyphenation/de.pat");
+// The embedded Language data (`language-data/` of craft-i18n, see `build.rs`); each is empty when
+// it isn't embedded. The TeX files are hyph-utf8's `hyph-pl.tex`, `hyph-pt.tex`, `hyph-it.tex` and
+// `hyph-de-1996.tex` (reformed spelling), unmodified, their licence headers in the files.
+use crate::data::{DE_PAT, EN_US_DIC, EN_US_PAT, IT_PAT, PL_PAT, PT_PAT};
 
 impl Dictionary {
     /// The bundled US English dictionary (decoded on first use).
@@ -152,6 +144,10 @@ fn core_breaks(core: &[char], lang: ProofLang) -> (Vec<usize>, Source) {
         return (crate::ru::hyphen::points(core), Source::Heuristic);
     }
     let dict = Dictionary::en_us();
+    // No English Language data embedded: hyphenation is off.
+    if dict.is_empty() && Patterns::en_us().is_empty() {
+        return (vec![], Source::None);
+    }
     let s: String = core.iter().collect();
     let from_mask = |m: u64, len: usize| (1..len.min(64)).filter(|&i| m & (1 << i) != 0).collect::<Vec<_>>();
     if let Some(m) = dict.get(&s) {
@@ -178,6 +174,10 @@ fn core_breaks(core: &[char], lang: ProofLang) -> (Vec<usize>, Source) {
 /// Polish: exception words, then the patterns, then the Polish syllable heuristic.
 fn core_breaks_pl(core: &[char]) -> (Vec<usize>, Source) {
     let pats = Patterns::pl();
+    // No Polish patterns embedded: hyphenation is off.
+    if pats.is_empty() {
+        return (vec![], Source::None);
+    }
     let s: String = core.iter().collect();
     if let Some(p) = pats.exception(&s) {
         return (p.to_vec(), Source::Dictionary);
@@ -193,6 +193,10 @@ fn core_breaks_pl(core: &[char]) -> (Vec<usize>, Source) {
 /// [`core_breaks_pl`] for a language with bundled patterns (Portuguese, Italian, German): its
 /// exception words, the patterns, then the generic heuristic.
 fn core_breaks_patterns(pats: &Patterns, core: &[char]) -> (Vec<usize>, Source) {
+    // The language's patterns aren't embedded: hyphenation is off.
+    if pats.is_empty() {
+        return (vec![], Source::None);
+    }
     let s: String = core.iter().collect();
     if let Some(p) = pats.exception(&s) {
         return (p.to_vec(), Source::Dictionary);
@@ -462,12 +466,14 @@ mod tests {
         hyphenate_word(w, &Limits::default())
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn bundled_data_loads() {
         assert!(Dictionary::en_us().len() > 150_000, "{}", Dictionary::en_us().len());
         assert!(Patterns::en_us().len() > 1000, "{}", Patterns::en_us().len());
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn dictionary_words() {
         assert_eq!(h("happen"), "hap-pen");
@@ -481,6 +487,7 @@ mod tests {
         assert_eq!(word_breaks("publication").1, Source::Dictionary);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn case_apostrophes_and_punctuation() {
         assert_eq!(h("Typography"), "Ty-pog-ra-phy");
@@ -494,6 +501,7 @@ mod tests {
         assert_eq!(h("typography-composition"), "ty-pog-ra-phy-com-po-si-tion");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn inflections_inherit_the_stem() {
         assert_eq!(h("ripples"), "rip-ples");
@@ -501,6 +509,7 @@ mod tests {
         assert_eq!(h("restrained"), "re-strained");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn patterns_cover_unknown_words() {
         // Not in the word list: the trained patterns decide.
@@ -686,6 +695,7 @@ mod tests {
         }
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn hyphenating_a_long_word_is_linear() {
         // A word of n letters against one of 8n: linear ~8x the cost, the old rescans ~64x. One in
@@ -748,6 +758,7 @@ mod tests {
         hyphenate_word_in(w, &Limits::default(), ProofLang::Pl)
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn polish_patterns_load() {
         let p = Patterns::pl();
@@ -764,6 +775,7 @@ mod tests {
         hyphenate_word_in(w, &Limits::default(), ProofLang::It)
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn italian_patterns_load() {
         let p = Patterns::it();
@@ -772,6 +784,7 @@ mod tests {
         assert_eq!(p.exception_count(), 0);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn italian_words_hyphenate_by_italian_rules() {
         for (w, want) in [
@@ -798,6 +811,7 @@ mod tests {
         assert_eq!(word_breaks_in("famiglia", ProofLang::It).1, Source::Patterns);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn portuguese_patterns_load() {
         let p = Patterns::pt();
@@ -809,6 +823,7 @@ mod tests {
         assert_eq!(p.exception("software"), Some(&[4][..]));
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn portuguese_words_hyphenate_by_portuguese_rules() {
         for (w, want) in [
@@ -828,6 +843,7 @@ mod tests {
         }
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn polish_words_hyphenate_by_polish_rules() {
         for (w, want) in [
@@ -861,6 +877,7 @@ mod tests {
         assert_eq!(word_breaks_in("konstytucja", ProofLang::Pl).1, Source::Patterns);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn polish_heuristic_for_foreign_letters() {
         // Letters outside the Polish alphabet: the Polish syllable heuristic, digraphs kept whole.
@@ -882,6 +899,7 @@ mod tests {
         }
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn german_patterns_load() {
         let p = Patterns::de();
@@ -890,6 +908,7 @@ mod tests {
         assert_eq!(p.exception_count(), 0);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn german_words_follow_the_german_patterns() {
         let de = |w: &str| hyphenate_word_in(w, &Limits::default(), ProofLang::De);
diff --git a/crates/proof/src/lib.rs b/crates/proof/src/lib.rs
index bf2cde13..a917f217 100644
--- a/crates/proof/src/lib.rs
+++ b/crates/proof/src/lib.rs
@@ -1,9 +1,9 @@
-//! WordCraft proofing, per language. A run's language (its BCP 47 tag) picks the tools through
+//! Proofing for the Craft Apps (moved from WordCraft's `wordcraft-proof`), per language. A run's language (its BCP 47 tag) picks the tools through
 //! [`ProofLang`]; the `*_in` functions take it, the older English-only ones remain.
 //!
 //! - **English** ([`ProofLang::En`]; also text with no language): spelling against the
 //!   public-domain Moby word list (~160k words, the same list that drives hyphenation) plus our
-//!   supplement of modern words it lacks (`assets/spelling/en-extra.txt`: `desktop`, `email`,
+//!   supplement of modern words it lacks (craft-i18n's `language-data/en-us/en-extra.txt`: `desktop`, `email`,
 //!   `download`…), with inflections (`-s`, `-es`, `-ed`, `-ing`, `-ly`, `'s`…), a user dictionary and ignore lists;
 //!   suggestions by edit distance. Grammar checks that are cheap and reliable: repeated words,
 //!   `a`/`an`, capital letter after a sentence end, spaces before punctuation, doubled spaces.
@@ -47,9 +47,19 @@
 //!   Italian, German), Bulgarian syllable rules, Russian word-division rules, heuristic.
 //!
 //! [`check_text`] checks a paragraph whose runs are in different languages.
+//!
+//! **Language data** (the Moby word list, the pattern files, our word supplements) is embedded at
+//! build time from craft-i18n's `language-data/` (`CRAFT_I18N_DIR`, see `build.rs`). A build
+//! without it has none: English spelling marks nothing and has no suggestions, and hyphenation
+//! that needs the data is off; grammar and the rule-based hyphenation (Bulgarian, Turkish,
+//! Russian) are code and still work.
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
 pub mod affix;
+/// The Language data embedded from craft-i18n by `build.rs` (each constant empty when it isn't).
+mod data {
+    include!(concat!(env!("OUT_DIR"), "/language_data.rs"));
+}
 pub mod bg;
 pub mod cs;
 pub mod dict;
@@ -339,7 +349,7 @@ const COMMON: &str = "a an the and or but if of to in on at by for with from as
 
 /// Our supplement of common words the Moby list lacks (`desktop`, `email`, `download`…): one
 /// lowercase base form per line, `#` comments. Inflections come from [`known_core`].
-const EXTRA_EN: &str = include_str!("../../../assets/spelling/en-extra.txt");
+use data::EXTRA_EN;
 
 fn extra_words() -> &'static HashSet<&'static str> {
     static E: OnceLock<HashSet<&str>> = OnceLock::new();
@@ -496,8 +506,17 @@ fn accepted_by_options(word: &str, opts: &Options) -> bool {
         || in_user_dictionary(&w.to_lowercase())
 }
 
+/// Is the English word list embedded? Without it English can't be checked, so every English
+/// word counts as correct (no red underlines), as in a language without a dictionary.
+fn english_data() -> bool {
+    !dict::Dictionary::en_us().is_empty()
+}
+
 /// [`is_correct`] with the File › Options › Proofing choices.
 pub fn is_correct_with(word: &str, opts: &Options) -> bool {
+    if !english_data() {
+        return true;
+    }
     let w = word.trim_matches(|c: char| !c.is_alphanumeric() && c != '\'');
     let w = w.trim_matches('\'');
     if accepted_by_options(w, opts) {
@@ -578,6 +597,9 @@ fn english_preferred(lower: &str, lang: ProofLang) -> Option<String> {
 /// (`colour` in American English, `color` in British), plus this dialect's spellings of the
 /// list's words ([`en_variants`]). The user dictionary overrules both.
 fn is_correct_english(word: &str, lang: ProofLang, opts: &Options) -> bool {
+    if !english_data() {
+        return true;
+    }
     let w = word.trim_matches(|c: char| !c.is_alphanumeric() && c != '\'').trim_matches('\'');
     if accepted_by_options(w, opts) {
         return true;
@@ -1016,6 +1038,11 @@ fn starts_consonant_sound(w: &str) -> bool {
     ["uni", "use", "usu", "eu", "one", "once", "ubiq", "uti", "ure", "uro"].iter().any(|p| l.starts_with(p))
 }
 
+/// The no-Language-data build (`build.rs` sets `craft_proof_data` when the English word list is
+/// embedded).
+#[cfg(all(test, not(craft_proof_data)))]
+mod no_data;
+
 #[cfg(test)]
 mod tests {
     #[test]
@@ -1161,11 +1188,13 @@ mod tests {
         assert_eq!(grammar("elma ve armut. sonra kiraz", ProofLang::Tr, true), ["sonra"]);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn dictionary_loads() {
         assert!(dict::Dictionary::en_us().len() > 100_000);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn spelling() {
         for w in [
@@ -1196,6 +1225,7 @@ mod tests {
     }
 
     /// #1694: `-ically` adverbs come from their `-ic` adjective (specific → specifically).
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn ically_adverbs_are_known() {
         for w in ["specifically", "scientifically", "automatically", "dramatically", "Specifically"] {
@@ -1208,6 +1238,7 @@ mod tests {
 
     /// #1694 review: only `-ic` adjectives take `-ally`; other known words (dictionary or
     /// supplement) don't.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn non_ic_words_do_not_take_ally() {
         for (base, wrong) in [("desktop", "desktopally"), ("house", "houseally"), ("final", "finalally"), ("green", "greenally")] {
@@ -1217,6 +1248,7 @@ mod tests {
     }
 
     /// #520: common modern words (and their inflections) are known; misspellings still flagged.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn common_modern_words() {
         for w in [
@@ -1253,6 +1285,7 @@ mod tests {
 
     /// The supplement stays a sorted list of lowercase base forms.
     /// #40: British spellings and their inflections are not flagged.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn british_spellings_are_known() {
         for w in [
@@ -1299,6 +1332,7 @@ mod tests {
 
     /// Each English accepts its own spellings and flags the other dialect's, suggesting its own
     /// first, as Word does (#1281, #1045).
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn english_dialects_flag_each_others_spellings() {
         let (us, gb, ca) = (ProofLang::En, ProofLang::EnGb, ProofLang::EnCa);
@@ -1391,6 +1425,7 @@ mod tests {
 
     /// The words #40 (folded into #1281) reported as flagged in British English, with their
     /// inflections: right in en-GB, and in en-US flagged or not as `en-variants.txt` decides.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn british_words_reported_in_issue_40_are_right_in_en_gb() {
         let (us, gb, ca) = (ProofLang::En, ProofLang::EnGb, ProofLang::EnCa);
@@ -1470,6 +1505,7 @@ mod tests {
         assert!(check_spelling_in(text, gb).is_empty(), "{:?}", check_spelling_in(text, gb));
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn user_dictionary_accepts_the_other_dialects_spelling() {
         add_word("savour");
@@ -1479,6 +1515,7 @@ mod tests {
         assert!(!is_correct_in("savour", ProofLang::En));
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn supplement_is_sorted_lowercase() {
         let words: Vec<&str> = EXTRA_EN.lines().filter(|l| !l.is_empty() && !l.starts_with('#')).collect();
@@ -1487,6 +1524,7 @@ mod tests {
         assert!(words.iter().all(|w| w.chars().all(|c| c.is_lowercase() || c == '\'' || c == '-')), "not lowercase");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn spelling_issues_in_text() {
         let t = "This sentense has a mispelled word, see https://example.com/xyzq.";
@@ -1495,6 +1533,7 @@ mod tests {
         assert_eq!(bad, vec!["sentense", "mispelled"]);
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn address_token_covers_every_word_split_out_of_it() {
         // #1335: one whitespace-delimited token, however punctuation splits it, has one
@@ -1509,6 +1548,7 @@ mod tests {
         assert_eq!(bad.last(), Some(&"wugwug"), "{bad:?}");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn address_after_a_wide_space_is_an_internet_token() {
         // A web or e-mail address after a no-break space or an ideographic space is skipped,
@@ -1521,6 +1561,7 @@ mod tests {
         assert!(["xyzq", "blorp", "qwirpy", "zxq", "wugwug"].iter().all(|w| bad.contains(w)), "{bad:?}");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn spelling_scales_over_one_long_token() {
         // #1335: thousands of punctuation-separated words inside a single
@@ -1582,6 +1623,7 @@ mod tests {
         }
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn user_dictionary_works() {
         assert!(!is_correct("zxqwordcrafty"));
@@ -1590,6 +1632,7 @@ mod tests {
     }
 
     /// #40: the user dictionary survives a save and a fresh load.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn user_dictionary_persists_through_a_file() {
         let dir = std::env::temp_dir().join(format!("wc-dict-{}-{}", std::process::id(), "persist"));
@@ -1612,6 +1655,7 @@ mod tests {
     }
 
     /// #40: a hostile file is capped: invalid lines are skipped, and only the first megabyte is read.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn hostile_dictionary_files_are_capped() {
         let dir = std::env::temp_dir().join(format!("wc-dict-{}-{}", std::process::id(), "hostile"));
@@ -1634,6 +1678,7 @@ mod tests {
     }
 
     /// #40: saving merges in words another process saved, and leaves out the ones just removed.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn saving_merges_with_the_file() {
         let dir = std::env::temp_dir().join(format!("wc-dict-{}-{}", std::process::id(), "merge"));
@@ -1651,6 +1696,7 @@ mod tests {
     }
 
     /// Ignore All lasts for the session: the word is accepted but isn't in the dictionary.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn ignored_words_are_not_dictionary_words() {
         assert!(!is_correct("zxqignoredword"));
@@ -1749,6 +1795,7 @@ mod tests {
     }
 
     /// #100: runs in a language without a dictionary are never flagged; English still is.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn non_english_words_are_not_flagged() {
         for w in ["ąžuolas", "élève", "über", "labas", "bonjour"] {
@@ -1761,6 +1808,7 @@ mod tests {
     }
 
     /// File › Options › Proofing (#485): each "Ignore" choice turned off makes those words count.
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn ignore_options_decide_what_is_checked() {
         let t = "SENTENSE helo2 www.exampel.org";
@@ -1772,6 +1820,7 @@ mod tests {
         assert!(is_correct_with("NASA", &all), "capitals that are a word stay correct");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn hyphenation() {
         let l = hyphen::Limits::default();
@@ -1782,6 +1831,7 @@ mod tests {
         v.iter().filter(|i| i.kind == IssueKind::Spelling).map(|i| t[i.start..i.end].to_string()).collect()
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn each_language_uses_its_own_tools() {
         pl::test_dict::install();
@@ -1802,6 +1852,7 @@ mod tests {
         assert!(!g.iter().any(|i| i.message.contains("\"an\"")), "{g:?}");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn italian_uses_its_own_tools() {
         it::test_dict::install();
@@ -1817,6 +1868,7 @@ mod tests {
         assert!(g.iter().any(|i| i.message.contains("ripetuta")), "{g:?}");
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn mixed_language_paragraphs_check_each_run_in_its_language() {
         pl::test_dict::install();
diff --git a/crates/proof/src/no_data.rs b/crates/proof/src/no_data.rs
new file mode 100644
index 00000000..c2cdc53e
--- /dev/null
+++ b/crates/proof/src/no_data.rs
@@ -0,0 +1,147 @@
+//! A build with no Language data embedded (no `CRAFT_I18N_DIR`): every public entry point still
+//! works and never panics. English spelling marks nothing and suggests nothing, hyphenation that
+//! needs the data is off, and grammar (code, not data) still works.
+
+use crate::hyphen::{self, Limits, Source};
+use crate::{Options, ProofLang, dict, en_variants, patterns};
+
+const LANGS: [ProofLang; 18] = [
+    ProofLang::En,
+    ProofLang::EnGb,
+    ProofLang::EnCa,
+    ProofLang::Pl,
+    ProofLang::Bg,
+    ProofLang::Pt,
+    ProofLang::It,
+    ProofLang::Hr,
+    ProofLang::Tr,
+    ProofLang::Ru,
+    ProofLang::Cs,
+    ProofLang::Id,
+    ProofLang::Es,
+    ProofLang::EsMx,
+    ProofLang::Es419,
+    ProofLang::EsUy,
+    ProofLang::De,
+    ProofLang::Other,
+];
+
+/// Words and text that exercise each entry point, hostile ones included.
+const SAMPLES: [&str; 10] = [
+    "",
+    "teh colour of hyphenation",
+    "Ünïcödé — ‘quotes’ don't",
+    "a a  apple .Next sentence",
+    "https://example.org a@b.org",
+    "zażółć gęślą jaźń",
+    "Привет, мир — кто-то",
+    "¿Qué tal? más",
+    "\u{0}\u{FFFF}\u{10FFFF}",
+    "supercalifragilisticexpialidociousxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
+];
+
+#[test]
+fn nothing_is_embedded() {
+    assert!(crate::data::EN_US_DIC.is_empty());
+    assert!(dict::Dictionary::en_us().is_empty());
+    for p in [patterns::Patterns::en_us(), patterns::Patterns::pl(), patterns::Patterns::pt(), patterns::Patterns::it(), patterns::Patterns::de()] {
+        assert!(p.is_empty());
+        assert_eq!(p.exception_count(), 0);
+    }
+}
+
+#[test]
+fn english_spelling_marks_nothing_and_suggests_nothing() {
+    for w in ["teh", "colour", "color", "zxqv", "desktop"] {
+        assert!(crate::is_correct(w), "{w}");
+        assert!(crate::is_correct_with(w, &Options::default()), "{w}");
+        assert!(crate::is_correct_for(w, Some("en-GB")), "{w}");
+        for l in [ProofLang::En, ProofLang::EnGb, ProofLang::EnCa] {
+            assert!(crate::is_correct_in(w, l), "{w} {l:?}");
+            assert!(crate::suggest_in(w, 5, l).is_empty(), "{w} {l:?}");
+        }
+        assert!(crate::suggest(w, 5).is_empty(), "{w}");
+        assert_eq!(en_variants::preferred(w, ProofLang::En), None);
+        assert!(!en_variants::is_foreign(w, ProofLang::EnGb));
+    }
+    assert!(crate::check_spelling("Teh colour of zxqv").is_empty());
+    assert!(crate::check_spelling_in("Teh colour", ProofLang::EnGb).is_empty());
+}
+
+#[test]
+fn grammar_still_works() {
+    assert!(!crate::check_grammar("This is is wrong.").is_empty());
+}
+
+#[test]
+fn hyphenation_is_off_where_it_needs_data() {
+    let lim = Limits::default();
+    for (w, l) in [
+        ("hyphenation", ProofLang::En),
+        ("hyphenation", ProofLang::Cs),
+        ("przedsiębiorstwo", ProofLang::Pl),
+        ("computador", ProofLang::Pt),
+        ("calcolatore", ProofLang::It),
+        ("Silbentrennung", ProofLang::De),
+    ] {
+        assert_eq!(hyphen::word_breaks_in(w, l), (vec![], Source::None), "{w} {l:?}");
+        assert!(hyphen::hyphen_points_in(w, &lim, l).is_empty(), "{w} {l:?}");
+        assert_eq!(hyphen::hyphenate_word_in(w, &lim, l), w);
+    }
+    assert!(hyphen::hyphen_points("hyphenation", &lim).is_empty());
+    assert_eq!(hyphen::hyphenate_word("hyphenation", &lim), "hyphenation");
+    assert_eq!(hyphen::word_breaks("hyphenation").1, Source::None);
+    // Rules are code, not data: Bulgarian still hyphenates.
+    assert!(!hyphen::word_breaks_in("книжарница", ProofLang::Bg).0.is_empty());
+}
+
+/// Every public entry point, in every language, on every sample: no panic.
+#[test]
+fn every_public_function_runs_without_data() {
+    let lim = Limits { min_word: 0, after_first: 0, before_last: 0, capitalized: true };
+    let opts = Options { ignore_uppercase: false, ignore_numbers: false, ignore_internet: false };
+    for text in SAMPLES {
+        let len = text.len();
+        let _ = crate::words(text);
+        let _ = crate::check_spelling(text);
+        let _ = crate::check_spelling_with(text, &opts);
+        let _ = crate::check_grammar(text);
+        let _ = crate::is_correct(text);
+        let _ = crate::is_correct_with(text, &opts);
+        let _ = crate::suggest(text, 5);
+        let _ = crate::custom_word(text);
+        let _ = crate::has_dictionary(Some(text));
+        let _ = crate::missing_dictionary(Some(text));
+        let _ = crate::unreadable_dictionary(Some(text));
+        let _ = crate::is_correct_for(text, Some(text));
+        let _ = hyphen::word_breaks(text);
+        let _ = hyphen::hyphen_points(text, &lim);
+        let _ = hyphen::hyphenate_word(text, &lim);
+        let spans: Vec<(std::ops::Range<usize>, ProofLang)> = LANGS.iter().map(|&l| (0..len, l)).collect();
+        let _ = crate::check_text(text, &spans);
+        let _ = crate::check_text_with(text, &spans, &opts, true, true);
+        // Out-of-range and reversed spans are hostile input too.
+        #[allow(clippy::reversed_empty_ranges)]
+        let _ = crate::check_text(text, &[(len + 5..len + 9, ProofLang::En), (3..1, ProofLang::Pl)]);
+        for l in LANGS {
+            let _ = crate::check_spelling_in(text, l);
+            let _ = crate::check_grammar_in(text, l);
+            let _ = crate::is_correct_in(text, l);
+            let _ = crate::is_correct_in_with(text, l, &opts);
+            let _ = crate::suggest_in(text, 5, l);
+            let _ = crate::dictionary_load_error(l);
+            let _ = hyphen::word_breaks_in(text, l);
+            let _ = hyphen::hyphen_points_in(text, &lim, l);
+            let _ = hyphen::hyphenate_word_in(text, &lim, l);
+            let _ = en_variants::preferred(text, l);
+            let _ = en_variants::is_foreign(text, l);
+            let _ = en_variants::known_variant(text, l, |_| true);
+        }
+    }
+    let _ = crate::installed_dictionaries();
+    let _ = crate::dictionary_generation();
+    let _ = crate::user_dictionary();
+    let _ = crate::has_dictionary(None);
+    let _ = crate::missing_dictionary(None);
+    let _ = crate::unreadable_dictionary(None);
+}
diff --git a/crates/proof/src/ru/extra.rs b/crates/proof/src/ru/extra.rs
index 95397e61..d9c992ae 100644
--- a/crates/proof/src/ru/extra.rs
+++ b/crates/proof/src/ru/extra.rs
@@ -1,11 +1,11 @@
 //! Our supplement of Russian words older Hunspell dictionaries lack (`маркетплейс`, `промокод`,
-//! `интеграция`, `бонусный`…), from `assets/spelling/ru-extra.txt`: each base form with its
+//! `интеграция`, `бонусный`…), from craft-i18n's `language-data/ru/ru-extra.txt`: each base form with its
 //! declension, expanded here into every form.
 
 use std::collections::HashSet;
 use std::sync::OnceLock;
 
-const EXTRA_RU: &str = include_str!("../../../../assets/spelling/ru-extra.txt");
+use crate::data::EXTRA_RU;
 
 /// Every form of the supplement: common words (lower case) and names (lower case too, but they
 /// only match a word written with a capital).
@@ -156,6 +156,7 @@ fn forms(base: &str, class: &str) -> Vec<String> {
 mod tests {
     use super::*;
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn supplement_words_decline() {
         for w in [
diff --git a/crates/proof/src/ru/mod.rs b/crates/proof/src/ru/mod.rs
index c92e2712..504c3853 100644
--- a/crates/proof/src/ru/mod.rs
+++ b/crates/proof/src/ru/mod.rs
@@ -399,6 +399,7 @@ mod tests {
         assert!(suggest::suggest_in(&none, "превет", 5).is_empty());
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn russian_words_are_correct() {
         test_dict::install();
diff --git a/crates/proof/src/vi.rs b/crates/proof/src/vi.rs
index 1abf7d4a..0276fd00 100644
--- a/crates/proof/src/vi.rs
+++ b/crates/proof/src/vi.rs
@@ -83,6 +83,7 @@ mod checker_tests {
         assert!(check_text_with(text, &[], &Options::default(), true, false).is_empty());
     }
 
+    #[cfg_attr(not(craft_proof_data), ignore = "needs the Language data (CRAFT_I18N_DIR)")]
     #[test]
     fn english_keeps_its_marks_and_skips_vietnamese_names() {
         let text = "We met Nguyễn yesterdy at the office.";